Research on Key Factors of Sealing Performance of Combined Sealing Ring

In this study, the mechanical properties of a combined seal ring under different loads were numerically calculated using ANSYS. The effect of the working pressure and pre-compression ratio of a rubber O-ring on the contact stress of the combined seal ring was studied. The influence of the wear ring’s chamfer, thickness, and width on the contact stress and contact force of the combined seal ring was analyzed. Studies have shown that it is particularly important to select a compression ratio that is suitable for the working conditions. Under the same conditions of working pressure and compression ratio, upon increasing the wear ring chamfer, the contact pressure is decreased due to the decreasing contact bandwidth between the wear ring and the cylinder wall. This has little effect on the contact stress of the combined seal ring as well as the contact force, while the width of the wear ring is proportional to the latter.

Development and Application of a New Type of Medical Protective Sputum Suction Respiratory Circuit

Background: At present, there are few breathing circuits that can protect health care workers. Here, we have developed a new disposable medical protective sputum suction breathing circuit.Methods：The main components of the structure of the novel medical protective breathing circuit are adapter, isolation sleeve, stop sleeve, sealing cover and sealing ring. An isolation sleeve is inserted into the conversion joint. The isolation sleeve inner sleeve has a stop sleeve with an inverted round table structure. The upper nozzle of the adapter is provided with a sealing ring tightly combined with the lower outer edge of the isolation sleeve, and a sealing cover is provided on the sealing ring.Results: The device is easy to operate and can prevent the pollution caused by sputum splashing when sucking sputum.Conclusion: The medical protective sputum suction and breathing circuit is simple in structure, easy to use, and can effectively protect medical staff.

Dynamic failure analysis of static seals under pressure fluctuation in an ultrahigh-pressure water piston pump

For ultrahigh-pressure piston pumps, in the reciprocating action of the piston, the fretting between the static face seal and the mating surface occurs with the change of the pressure in the piston chamber. This phenomenon will seriously affect the service life of the seal ring and lead to the failure of the pump. However, the failure of static seals used to seal ultrahigh-pressures is usually studied from the directions of shear, stress, or rubber material. These studies cannot explain the failure phenomenon of the sealing ring found in our experiment. This paper analyzed the failure of the face seal ring in a piston pump with a maximum pressure of 120 MPa. A two-dimensional axisymmetric finite element model was established based on the Mooney-Rivlin constitutive relation of the rubber material, and the fretting conditions of the sealing ring were analyzed. Combined with the wear scars observed by the scanning electron microscope the face seal ring’s dynamic failure mechanism on the ultrahigh-pressure piston pump was determined. A better sealing scheme was proposed and verified by the duration test of the pump, which provided a basis for the design of the sealing of the ultrahigh-pressure fluid with high-frequency fluctuations.

Study on Improving the Sealing Reliability of Fluid Connector

Aiming at the problem of sealing reliability of fluid connector products commonly used in hydraulic system, this paper studies the static seal and the sliding seal. The factors affecting the sealing such as spring force, sealing ring and life of spring are considered one by one and the sealing effect is teseted. The results showed that improved fluid connector can ensure that the hydraulic system is in the state of not even air intake or oil leakage while connecting and disconnecting at any time. The connector has been successfully applied to a certain model of launch vehicle.

Fretting Wear of Rubber Sealing Ring Caused by Fluid Pressure Fluctuation

In the process of gas charging and discharging of gas cylinder, the fluid pressure fluctuates causing fretting wear of rubber sealing ring, which affects the sealing performance. The model of O-ring that installed at the mouth of the gas cylinder was established to study the fretting wear in the static seal. Effects of fluid pressure, compression ratio, friction coefficient and temperature on the fretting wear of the O-ring were considered. The results show that the fretting wear of O-ring can be divided into non-contact region, slip region and sticky region. In the static seal, the compression ratio and friction coefficient are the main factors affecting the fretting wear. The sealing performance is greatly influenced on the compression ratio and it is less affected by the temperature. The junction of slip region and sticky region has the greatest probability of seal failure.

Identification of the Effect of Ultrasonic Friction Reduction in Metal-Elastomer Contacts Using a Two-Control-Loop Tribometer

Pneumatic cylinders are widely used in highly dynamic processes, such as handling and conveying tasks. They must work both reliably and accurately. The positioning accuracy suffers from the stick-slip effect due to strong adhesive forces during the seal contact and the associated high breakaway forces. To achieve smooth motion of the piston rod and increased position accuracy despite highly variable position dynamics, sliding friction and breakaway force must be reduced. This contribution presents a specially designed linear tribometer that has two types of control. Velocity control allows the investigation of sliding friction mechanisms. Friction force control allows investigation of the breakaway force. Due to its bearing type, the nearly disturbance-free detection of stick-slip transients and the dynamic contact behavior of the sliding friction force was possible. The reduction of the friction force was achieved by a superposition of the piston rod’s movement by longitudinal ultrasonic vibrations. This led to significant reductions in friction forces at the rubber/metal interface. In addition, the effects of ultrasonic frequency and vibration amplitude on the friction reduction were investigated. With regard to the breakaway force, significant success was achieved by the excitation. The force control made it possible to identify the characteristic movement of the sealing ring during a breakaway process.

NUMERICAL AND ANALYTICAL MODELING OF STRESS-DEFORMED STATE OF THE METAL RING SEAL OF THE TUBING HAGER

The article presents a numerical and analytical modeling of the stress-strain state of a metal ring seal of a tubing hanger under installation loads, as well as under the influence of well pressure. An analytical method for calculating strength and tightness within the elastic formulation is proposed. The calculation by the finite element method was carried out in order to take into account plastic deformations, which make it possible to study the influence of the geometry of the contact zone of the sealing ring on the width of the contact pad and the magnitude of the contact pressure. Comparison of the calculation results by the analytical method and the finite element method is carried out. It is shown that the analytical method, as less labor-intensive, can be used at the initial stages of designing this type of equipment.

Investigation of local hot spots in sealing rings with different sealing materials

The local high temperature in the sealing pair is prone to cause local wear, which easily leads to seal failure. In this paper, a numerical method based on the finite element method is proposed to investigate the local high-temperature hot spot in a sealing ring with different sealing materials. The distribution of hot spots on the sealing surface is visualized by numerical computations. The critical speeds of the hot spot for the metal, composite, and powder metallurgical sealing materials are obtained under different friction coefficients. Based on the obtained results, the quantitative correlation between the critical speed of the hot spot and elastic modulus, thermal conductivity, specific heat capacity, thermal expansion coefficient, and seal sizes is determined. Then, a test method is designed to evaluate the thermal instability of the sealing ring. Scanning electron microscopy is utilized to examine the surface morphology of the sealing rings after the hot spots appear. The results of the present study demonstrate that the proposed method is consistent with the experiment. It indicates the effectiveness of the simulation method for investigating local hot spots in the sealing ring.